->There's a discussion of this over on rec.crafts.metalworking, started
->by the usual question of "is PVC OK". The concensus is still no,
->but a new reason or three have cropped up:
->* PVC brittles with age; the plasticizer evaporates over time
->* Oil in the compressed air attacks the plasticizer
->* Compressed gasses store much more energy than uncompressed liquids,
-> so failure is much more catastrophics (the "grenade" effect)
->* PVC pipe melts in a fire, leading to hazardous conditions for firefighters
->This last reason is apparently why it is against many local, business
->and OSHA regulations.
Then why is is legal for h2o? This doesn't make sense....(and if you
think it won't melt with h2o in it, I can assure you from personal
experience, it does. Lead pipes full of water melt. Copper pipes full
of water melt. Iron ones seem to hold up a bit better, though they'll
usually still bend some...Of course it depends on the severity of a fire.)
I'll buy it's against OSHA, but more likely for the explosive failure mode.
I do however know that when I last spec'd air lines in a building, I
was not given a choice about materials by either the architect or the
contractor. We got Black Iron. Period. I think it's the Right Thing...
What we did in the theater was to build an air distribution system with
1.5" iron pipe and reduction couplings into the coupler bodies. In a
80'x250' building that's alot of additional storage capacity...
My garage? Probably be iron...It's cheap and it lasts forever. Yes, you
need to buy a boatload of fittings and it's a pain to work with
sometimes, but if you have a pipe threader, it's not quite so bad.
Right now, of course it's a 3/8" hose draped over whatever it is
that I'm working on...Soon. I need to pour the outside pad for the
compressor first. And a few other small tasks.